No damage was reported or expected.
The earthquake was centered at 39.782N 123.562W depth; or seven miles north-northwest of Laytonville, 47miles north-northwest of Ukiah, 64miles south-southeast of Fortuna, 75 miles northwest of Clearlake, and 138 miles northwest of Sacramento.
The earth moved at about 5.6 miles beneath the surface.
Laytonville is a community of about 1,200 people in Mendocino County.
Mendocino County is adjacent to Sonoma, Lake, Glenn, Tehama, Trinity and Humboldt counties.
The region is along the Maacama Fault, which the USGS described as "mostly a right-lateral strike-slip fault that lies north of Santa Rosa and the immediate San Francisco Bay Area and extends as far north as Ukiah. It connects to the Rodgers Creek Fault through a complex set of faults between Santa Rosa and Healdsburg, and is thought to be the northward continuation of the Hayward-Rodgers Creek Fault System."
Very little is known about the history of the fault, according to the USGS and "recurrence intervals are uncertain."